Apparatus to control gravitational movement of a gem stone polishing tang towards a stone polishing surface



Dec. 1, 1970 A. LEIBOWITZ APPARATUS TO CONTROL GRAVITATIONAL MOVEMENT OF A GEM STONE v POLISHING TANG TOWARDS A STONE POLISHING SURFACE Filed Dec. 18, 1967 M E3016 JOEZOU United States Patent U.S. Cl. 51--1Z5 Claims ABSTRACT OF THE DISCLOSURE A gem stone polishing machine is provided with a tang whose movements towards a polishing surface are cushioned by a liquid dashpot which communicates with an upstanding tube, with the vertical positioning thereof being automatically varied to adjust the position of balance of the dashpot.

This invention relates to apparatus for controlling movements of a component adapted to move under gravity.

The invention consists in control apparatus for a component adapted to move under gravity comprising a liquid dashpot assembly for controlling gravitational movement of the component and an upstanding tube in liquid communication with the dashpot through a flexible tube connection which can be used to adjust the position of balance of the dashpot plunger by vertical movement of the upstanding tube.

The invention will now be described by way of an example wtih reference to gem stone polishing apparatus illustrated in the attached drawings in which: in FIG. 1 is a semi-diagrammatic perspective view and FIG. 2 is an enlarged sectional view of a component of the apparatus shown in FIG. 1.

Generally, the apparatus comprises a horizontally extending arm or tang 1, pivoted adjacent its rear end and carrying at its front end a gem stone chuck or dop 2 which, by pivoting movements of the tang, can be brouhgt into and out of polishing engagement with an underlying rotary polishing wheel 3.

To control gravitational movements of the tang 1 towards the wheel and then during polishing, control apparatus is provided. The tank has, at an intermediate point in its length, a downwardly depending follower 4 resting on a plunger 5 of a mercury filled dashpot 6 below the tang for cushioning movements of the tang towards the wheel and for then controlling the polishing pressure by exerting a back pressure on the tang. The dashpot reservoir is connected via a flexible rubber tube 7 to an upstanding partially mercury filled tube 8 mounted for automatically controlled vertical movements as will be described. The flexible rubber tube is of suflicient length that when the upstanding tube is in its lowest position, the rubber tube forms a U extending below the level of the dashpot reservoir.

When the tang is off the dashpot plunger, the plunger will have a balanced rest position, depending on the position of the upstanding tube. It is necessary for cushioning movements of the tang on to the wheel that this rest position be such that when the tang is lowered, its follower engages the plunger before a gem in the chuck engages the wheel. Then, the weight of the tang on the plunger gradually depresses the plunger allowing the gem to contact the wheel until polishing is completed. If, however, the tang is light or counter-weighted, its pressure on the plunger may be insufiicient to move it sufliciently from its initial balanced position to enable the gem to come into contact with the wheel. Therefore, according to a prime feature of the invention, when the tang has moved down onto the plunger, the mercury column is automatically lowered a predetermined amount. This causes the length of flexible tube below the dashpot to increase and accordingly lower the balance level of the plunger dashpot, since liquid flows out of the dashpot into the U-tube. It will be appreciated that the rate of descent of the mercury column influences the rate of descent of the plunger introducing a further measure of control for the tang movement.

After polishing, when the tang is lifted ofl the wheel and dashpot, it is necessary to restore the initial balance level of the plunger, since otherwise on the succeeding descent of the tang, the gem may strike the wheel before the follower engages the plunger. Accordingly, when the tang lifts off the wheel, means is provided for automatically and quickly lifting the mercury col umn back to its original position causing liquid to flow from the U-tube into the dashpot reservoir to raise the plunger balance level.

An electric motor 9, having a control circuit operated by movements of the tang may be employed for automatically raising and lowering the mercury tube through a pulley and belt system .11.

According to a further feature of the invention, valve means may be included in the tube leading from the dashpot reservoir to enable liquid to flow more speedily into than out of the reservoir. For example, a valve 12 may comprise a body 13 with first outlet means 14 at its reservoir end, second outlet means 15 at its mercury column end, and a movable valve member 16, such as a ball, adapted when liquid is flowing from the reservoir to be urged towards the second outlet means and limit flow therethrough, and when liquid is flowing into the reservoir to be urged towards the first outlet means but allowing a great flow therethrough. This can be achieved, as shown, by differently configured ball retaining mountings 17 and 18.

I claim:

'1. A gem stone polishing apparatus including a stone polishing surface, a stone carrying tang mounted for movement under gravity towards the polishing surface, and control means for the tang, said control means comprising a liquid-dashpot assembly for cushioning the tang during movement towards the polishing surface, an upstanding tube and a flexible tube connection providing liquid communication between the dashpot and the upstanding tube for adjusting the position of balance of the dashpot plunger by vertical movement of the upstanding tube.

2. Control apparatus to control gravitational movement of a gem stone polishing tang towards a stone polishing surface, comprising a liquid dashpot assembly for cushioning the tang during movement towards the polishing surface, an upstanding tube, a flexible tube connection providing liquid communication between the dashpot and the upstanding tube for adjusting the position of balance of the dashpot plunger by vertical movement of the upstanding tube, and automatic means for lifting the upstanding tube when the tang is lifted away from the dashpot and for lowering the upstanding tube after the tang has been lowered onto the dashpot.

3. Apparatus as claimed in claim 2, wherein the upstanding tube is adapted to be lifted more quickly than it is lowered.

4. Apparatus as claimed in claim 1, having valve means to permit liquid to flow more rapidly into the dashpot than out of the dashpot.

5. Apparatus as claimed in claim 4, wherein the valve means comprises a valve body, a first outlet leading to the dashpot, a second outlet leading into said upstanding tube and a floating member adapted to assume a position partially blocking the second outlet when liquid flows out of the dashpot and to move away from said position when liquid flows into the dashpot.

References Cited UNITED STATES PATENTS 2,446,901 8/ 1948 Blaisdell.

FOREIGN PATENTS 520,607 6/1956 Belgium. 1,084,675 1/1955 France.

HAROLD D. WHITEHEAD, Primary Examiner U.S. Cl. X.R.

Dedication 3,543,447.Alec Leibo'witz, London, England. APPARATUS TO CONTROL GRAVITATIONAL MOVEMENT OF A GEM STONE POLISH- IN G TANG TOWARDS A STONE POLISHING SURFACE. Patent dated Dec. 1, 1970. Dedication filed Sept. 7, 1973, by the assignee, Spectrum Diamonds (Proprietary) Ltd. Hereby dedicates the entire remaining term of said patent to the Public.

[Oficial Gazette J anuary 8, 1974.] 

